Numerous window shades are presently available. Roller shades usually utilize a spring loaded roller which is mounted at the top of a window frame adjacent the window. A panel of material is wound onto the roller which can be unrolled to cover the window. Insulated shades that are quilted with spun batting or foam are more effective for saving energy, but they are bulky and they tend to wrinkle when they roll because the side nearest the roller must accommodate a smaller diameter than the opposite side. Round floating bottom rails have also been used with multiple layer shades with some success. Overall these shades are limited by the selection of fabrics that won't wrinkle and the cost of inventorying relatively expensive sandwiches. Another problem with insulating shades is their flat look that is not considered as aesthetically pleasing as a full undulating multi-faceted look provided by drapes and pleated shades. Finally, multi-layer or insulated shades are generally opaque or nearly so because of their multiple layer nature. Consequently, they are even more limited in the range of light control than most regular non louvered window coverings.
Another type of shade utilizes a pleated panel of material which stacks by folding in an accordion fashion. There may be a single layer of zigzag fabric or a zigzag layer with a tab extending off one side of each pleat. The top of the material is attached to a headrail mounted adjacent the window. A bottom rail is provided at the bottom of the material. A cord extends from the top rail through the material to the bottom rail for raising and lowering the pleated shade and for supporting the weight of the bottom rail which allows the fabric to maintain a fullness or three-dimensional character and to refold consistently when stacked. This type of shade is available in a variety of fabrics ranging from translucent to opaque. Because of their resilient nature, pleated shades are difficult to insulate, instead the art has developed honeycomb structures using two or three panels of pleated material. Although these panels can be made of different materials they are rigidly affixed to one another and cannot be moved relative to one another and are, therefore, limited in light control. Although the cells effectively reduce thermal convection, the connections between layers act as bridges for thermal conduction and are inviting burrows for insects. When condensation does occur, the moisture is trapped within the cell and often stains the fabric.
In U.S. Pat. No. 4,953,610 Phillips et al. disclose a double window shade assembly having two independently operable pleated shades located in a front to back relationship. They prefer the front shade to be made of substantially translucent or light passing material while the back shade is made of substantially opaque or light blocking material. The user of the window shade assembly is able to adjust one or both of the front and back shades to control where outside light is able to pass through the assembly. Sunlight may be blocked by the rear shade, pass through the front shade or pass directly into the room without obstruction from either shade. Because there are two adjacent pleated shades, the product is nearly twice as wide as single panel shade. Accordingly, this shade is not suitable for narrow window frames. The system of the '610 patent also includes a single head rail and a primary bottom rail. One cord passes from the head rail through the front shade to the primary bottom rail. A second cord passes from the headrail through the rear shade to the primary bottom rail. These two cords maintain the front shade a fixed distance from the rear shade. Because of this arrangement it is not possible to lower the rear shade without also lowering the front shade. The side edges of pleated-type shades have a zigzag three-dimensional character and are relatively delicate which makes them hard to positively seal for an air-tight energy-effective fit.
The art has recognized that convection currents will develop between window panes, between a window pane and a shade or between two window shade panels whenever the distance between them exceeds approximately 0.5". The currents transport heat across air spaces via gravitationally driven circulation reducing the thermal efficiency of the system. Such currents can be significantly reduced by closing at least portions of the gap between the two panels to a distance less than 0.5".
Roller shades are difficult to install when compared to a pleated shade because they are only supported at the ends and they must be hung plumb or be adjusted with shims in the roll of the fabric so that they roll evenly on the roller. It is common practice to leave a considerable clearance between the end brackets and the fabric to avoid abrading the edge of the fabric on the brackets. It is important to be able to inspect the roller as the shade is being operated, and to be able to shim the diameter of the tube or to adjust the relative position of at least one end bracket. It is an object of this invention to be able to install a single set of mounting brackets that can be mounted anywhere along the length of the headrail as is the common practice in pleated shades and which support the headrail of the pleated shade and the end brackets of the roller shade.
Although double panel window shades have been proposed, the art has not found a shade which combines both a pleated shade and roller shade in a compact, thermally efficient manner and in which the roller shade and pleated shade are truly independently operable and easily installed.